The four species of wild rice compose the genus Zizania, a group of grasses that grow in shallow water in small lakes and slow-flowing streams. Often, only the flowering head of wild rice rises above the water. True rice, genus Oryza, is also a grass; the two genera Oryza and Zizania are closely related, sharing the tribe Oryzeae. Three species of wild rice are native to North America:

Northern wild rice (Zizania palustris) is an annual plant native to the Great Lakes region of North America. Northern wild rice is the state grain of the U.S. state of Minnesota.

Wild rice (Z. aquatica), also an annual, grows in the Saint Lawrence River and on the Atlantic and Gulf coasts of the United States.

Texas wild rice (Z. texana) is a perennial plant only found in a small area along the San Marcos River in central Texas.

Texas wild rice is in danger of extinction due to loss of suitable habitat in its limited range and pollution. Manchurian wild rice has almost disappeared from the wild in its native range, but has been accidentally introduced into the wild in New Zealand and is considered an invasive species there.

Use as a grainThe seeds of the two annual species are the ones most commonly harvested as grain. Native Americans harvested wild rice by canoeing into a stand of plants, and bending and beating the ripe grain heads with the canoe paddles, so as to thresh the seeds into the canoe. The Ojibwa call this plant "manoomin" or "good berry". Some seeds fell to the muddy bottom to overwinter and germinate in the spring. Wild rice and maize are the only cereal crops native to North America. It is a favorite food of dabbling ducks and other aquatic wildlife.
Almost always sold as a dried whole grain, wild rice is high in protein, the amino acid lysine and dietary fiber, and low in fat. Like true rice, it does not contain gluten. It is also a good source of the minerals potassium and phosphorus, and the vitamins thiamine, riboflavin and niacin. Because commercial, paddy grown wild rice is harder and denser than true rice, it must be cooked longer to become soft enough to be eaten; it generally requires cooking for at least 45-60 minutes in a ratio of wild rice to water of approximately 1 to 3. Because of its comparatively high cost and chewy texture it is often cooked together with true rice, often in a ratio of true rice to wild rice of 8 to 1 or 4 to 1. Manoomin, on the other hand, is not nearly as hard as paddy rice, allowing it to be cooked in 15-30 minutes.

Because of its nutritional value and taste, wild rice increased in popularity in the late 20th century, and commercial cultivation began in the US and Canada to supply the increased demand. In the United States the main producers are California and Minnesota (where it is the official state grain) and it is mainly cultivated in paddy fields. Canadian wild rice is usually harvested from natural bodies of water; the province of Saskatchewan is the largest producer in Canada.

Manchurian wild rice, gathered from the wild, was once an important grain in ancient China. Because of the difficulty of its domestication, it gradually lost importance with increasing population density, as its habitat was converted for use in raising rice. It is now very rare in the wild, and its use as a grain has completely disappeared in China, though it continues to be cultivated for its stems.

Use as a vegetable
The swollen, crisp white stems of Manchurian wild rice are grown as a vegetable, popular in East and Southeast Asia. The swelling occurs because of infection with the smut fungus Ustilago esculenta. The fungus prevents the plant from flowering, so the crop is propagated asexually, the infection being passed from mother plant to daughter plant. Harvest must be made between about 120 days and 170 days after planting, after the stem begins to swell but before the infection reaches its reproductive stage, when the stem will begin to turn black and eventually disintegrate.
Importation of the vegetable to the United States is prohibited in order to protect North American species from the fungus.

Ornamental use
Wild rice is also grown as an ornamental plant in garden ponds.

Cultural use
Several Native American cultures, such as the Ojibwa, consider wild rice (known as manoomin in Ojibwa) to be a sacred component in their culture. The rice is harvested by hand, with two people sitting in a canoe, with one knocking rice into the canoe with a pole while the other paddles slowly. For these groups, this harvest is an important cultural (and often economic) event.